The predictive value of the halo sign in color Doppler ultrasonography of the temporal arteries for diagnosing giant cell arteritis.

OBJECTIVE: The diagnosis of giant cell arteritis (GCA) usually requires a temporal artery biopsy. Recently it has been reported that a periluminal dark halo, detected by color Doppler ultrasonography (US) of the temporal arteries, is a characteristic sign of GCA. We evaluated the predictive value of this dark halo sign in diagnosing GCA.

METHODS: During a period of 2 years 69 patients suspected of having GCA were examined by US of both temporal arteries. Temporal artery biopsy was performed in 32 of these patients. The diagnosis of GCA was made if a patient had a biopsy showing arteritis, or met all the following criteria: (1) American College of Rheumatology GCA classification criteria were fulfilled; (2) there was a prompt clinical response to treatment with 40-60 mg/day of prednisone; and (3) no other diagnosis related to the patient's symptoms was made during 6 month followup.

RESULTS: Periluminal dark halo was observed in 24 of 69 patients. GCA was diagnosed in 12 of them, giving a positive predictive value (PPV) of only 50%. No halo was detected in 45 cases of which only 2 had GCA, resulting in a high negative predictive value (NPV) of 96%. The sensitivity and specificity of the halo sign for diagnosing GCA were 86% and 78%, respectively.

CONCLUSION: The PPV of the halo sign in US of the temporal arteries is unsatisfactory for diagnosing GCA. However, the NPV is very high. Thus the lack of a halo can practically serve to rule out a diagnosis of GCA, and precludes the need for a biopsy in most instances.